There is a question asked which resembles yours. I have pasted my response to that question here.
Please, note this is a general response.
Death. This theme is brought out when Thoni tells the woman she longs for a country that is full of darkness. No one will be able to see another person in that dark country. And there will be no hurt. Darkness symbolizes death. She longs to be dead.
2. Superstition. An elder asks Nyobi to bless the traditional medicine so that it can be powerful to bring back Remi.
3. Racism. Omange narrating an incident of an African seen with an Indian woman. That African are criticized for being in a relationship with someone of a different color.
4. Religion Vs Politics. The leader telling the elders when Remi comes back, they should make sure he is not influenced by Christianity. Also, when the Pastor tells Nyobi when Remi comes back he shouldn't be influenced by the elders.
5. Wife inheritance. Remi's father cussing Remi for not accepting to inherit his dead brother's widow. Also, his mother pleading he does so according to the custom of Maria tribe. Also, the elders pleading.
Another theme is:
6. Tribalism. Remi, kneeling beside the corpse of Thoni, says that he thought he had come to break tribalism and customs but instead, it lead to her death. This signifies tribalism was a rift in that region.
Here is another theme:
7. Immorality. Remi knew that he was married but decided to engage in adultery. Even though he ran away from the village because he was forced to marry Thoni whom he thought never loved him. At least, he should have divorced her so as to engage in a relationship with Jane. The imagery that brings out this theme is Jane entering Remi's house and asking him if he is not ready to go to the night club. Also, where Remi reveals to Jane he has a wife in the village.